A student wearing smooth-soled shoes pushes horizontally on a large wooden crate of…
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A student wearing smooth-soled shoes pushes horizontally on a large wooden crate of mass 40kg that is initially at rest on a rough concrete floor. The crate accelerates at 0.60m/s2 away from the student while the student’s feet do not slip relative to the floor.
(1) Draw a clearly labeled free-body diagram for the crate. Include and name each force and identify the object exerting it.
(2) Draw a clearly labeled free-body diagram for the student considered as a single system (ignore internal forces). Include and name each external force and identify the object exerting it.
(3) Using your diagrams, describe how Newton’s third law accounts for the interaction forces between (i) the student and crate and (ii) the student and floor. Identify each action–reaction pair and explain why both members of a pair never appear on the same free-body diagram.